I find this an interesting argument by Matt Stoller. He looks at the election in California CD 50 and points out that Busby ran exactly the kind of election the Democratic powers-that-be in Washington suggessted. She avoided progressives and ran on competency and anti-corruption.
In the meantime, Bilbray talked up his progressive background. The district was gerrymandered for Republicans, and Bush carried it by 55%, so Busby had her work cut out for her. She lost.
Lesson? Per Stoller, progressive positions win elections, anti-corruption and emphasizing Republican failures and incompetence by themselves do not. Go check Stoller's argument.